Postpartum mares will have a “foal heat” 7 to 14 days following foaling, and a second cycle approximately 30 days later.

Breeding on foal heat is still somewhat of a controversial practice. Mares are usually bred on foal heat as long as three criteria are met.

1. The mare has a normal foaling, that is she does not have excessive bruising or tearing.
2. The mare does not retain the placenta for more three hours.
3. Upon palpation and ultrasound exam the uterus

External Reproductive Organs

Penis and Prepuce 

The stallion’s penis consists of 3 parts: (1) the root or bulb, (2) the body or shaft, (the main part), and (3) the glans, the enlarged free end of the penis. When not erect, the penis is 50 cm long and 2.5 to 6 cm in diameter with the distal end 15 to 20 cm free in the prepuce. When erect, the penis doubles in length and thickness and the glans increases by 3 …

Twinning in mares is very undesirable because of low survival rates, usually very weak foals, and numerous conformational problems. Of all twin pregnancies, 60% will birth a live single foal, 31% will abort both foals, and 9% will carry both twins to term. Of the 9% carried to term, 64.5% will birth two stillborn foals, 21% will birth one live foal and one stillborn foal and 14.5% will birth two live foals.

Origination-Dizygotic

Two separate ovulations occurring a day apart …

Many producers who raise horses find breeding horses rewarding, yet frustrating. Mares and stallions are traditionally placed in the breeding herd due to successful performance records, with little consideration for their reproductive capabilities. Horses are difficult breeders with an estimated foaling rate of below 60 percent. Various factors contribute to this and basic understanding of equine reproductive physiology can improve reproductive efficiency and foaling rates. The breeding manager’s goal should be to get the maximum number of mares pregnant, in …

Semen Collection 

Collection with a breeding phantom

In collecting semen from a stallion, a jump mare or breeding phantom is commonly used. Stallions can be easily trained to mount a breeding phantom. Those trained to mount a phantom make collection much safer and more consistent. The phantom should be designed to be comfortable for the stallion and should mimic the same angle as the mare. If a jump mare is used, she should be in good standing heat and have …

Gestation Length

The average gestation length (duration of pregnancy) of mares is 335 to 340 days, but can range from 320 to 370 days. There may be much variability among mares, but most individually follow similar patterns year after year. Foals are considered premature if delivered at less than 326 days of gestation and usually require immediate veterinary attention. Mares foaling before 310 days are considered to have aborted. Many breeders will calculate the expected foaling date at 11 months …

The signs of impending parturition are about as variable as gestation length. Although there is a tremendous amount of variation among mares, many individuals do repeat their foaling behavior year after year. Therefore, it is recommended to keep accurate records on each mare to aid future deliveries.

Waxing Teats 

The classical signs of approaching parturition include udder development beginning 2 to 6 weeks before foaling, then milk let down into the teats (teat distension) 4-6 days prior to parturition. Due …

Foal Behavior After Birth

The foal will usually stand within 30 minutes, typically after several failed attempts. As soon as it is steady on its feet, often within an hour of birth, the foal will attempt to nurse. Teat-seeking behavior is persistent, even somewhat random, because the foal does not know exactly where the teat is located. However, with the gentle assistance of the mare, the foal will find the teat, quickly understand its purpose, and know how to suckle, …

Teasing Mares

The teasing of a mare with a stallion is an important job in a breeding program as it allows breeding managers to determine the stage of an individual mare’s estrous cycle. Accurate determination of estrus (heat) allows breeding managers choose the best time to breed the …